Millions of Americans squeezing in a few days at the beach before schools open were warned Sunday that swells generated by the storm Ernesto, which strengthened into a hurricane again on Sunday, presented a severe danger to swimmers along much of the Atlantic coast.

The National Hurricane Center said "life-threatening surf and rip current conditions" are likely for the next few days and beachgoers should stay out of the water if advised by lifeguards. National Weather Service offices from Maine to Florida, warned of dangerous rip currents.

Ernesto, centered 520 miles south of Halifax, Canada, gained strength as its maximum sustained winds increased from 70 to 75 mph, just above the threshold for a Category 1 hurricane. The storm was headed north-northeast at 17 mph. Ernesto was forecast to pick up some speed and turn toward the east-northeast in the coming days.

At least three deaths have been blamed on Ernesto after two men drowned Friday off Hilton Head Island, South Carolina, and a swimmer was found unresponsive in the waters of Surf City, North Carolina, on Saturday. The hurricane center said dangerous surf and rip currents were also possible in the Bahamas, Bermuda, and Atlantic Canada during the next few days.

'Don’t become a statistic':Hurricane Ernesto brings rip current danger to millions

Developments:

∎ The New York City Department of Parks & Recreation banned swimming Sunday at beaches in Queens and Brooklyn.

∎ The center of weakened Ernesto figures to pass near southeastern Newfoundland in Canada from late Monday into Tuesday morning.

∎ In New Jersey, emergency management officials discouraged beachgoers from entering the water when lifeguards are not on duty: "Keep your feet in the sand until the lifeguards are on the stand!" Dozens of rescues were reported in recent days.

Third death because of rip currents reported

The National Weather Service has reported a third fatality because of rip currents generated by Ernesto along the Atlantic Coast.

Two rescue swimmers from the Surf City Fire Department in North Carolina responded to a call of a swimmer in distress Saturday at 2:46 p.m., the city said in a news release. The rescue swimmers found Sean Davis, 41, of Hampstead, North Carolina, unresponsive in the water. Life-saving measures were attempted on the beach, the city said, but Davis did not survive.

Elsewhere along the North Carolina coast Saturday, 23 rip current rescues were reported in Wrightsville Beach, five in Carolina Beach and another in Kure Beach, the weather service said. 

− Dinah Voyles Pulver

Rodanthe house collapses on Outer Banks

In the North Carolina Outer Banks town of Rodanthe, Chicamacomico Banks Fire & Rescue posted photos of the battered remains of a coastal house that was swept into the Atlantic Ocean. Numerous other homes are at risk of collapse from Ernesto, the agency said in a string of social media posts. The debris in the water added to the dangers to swimmers, the agency warned.

"High rip current risk in Rodanthe, waves and salvo today and tomorrow," the agency warned. "Entering the ocean is not advised."

How a rip current works

Rip currents are narrow, strong currents that quickly flow away from the shore. Typically, they move about 1 to 2 feet per second, but they could move as fast as 8 feet per second, or 5.5 mph, beyond any Olympic swimmer’s pace. They’re usually no wider than 80 feet.

Normally, when waves hit the beach, water flows back to the ocean uniformly. But low spots in the ocean floor, near surf or breaks in sandbars, disrupt that uniform return of water. This causes water to rush through one area to create that powerful rip current outward. If you're caught in a rip current, relax. Rip currents pull you out, not under. Float or tread water until you can escape or are rescued.

Bermuda largely spared from Ernesto's worst

Officials in Bermuda were counting their blessings after Ernesto caused less damage than expected before heading north.

Forecasts indicated Ernesto could reach the British island territory as a Category 3 hurricane with devastating winds of at least 111 mph after meandering for two days in the warm west-Atlantic waters. But the storm tamed down a bit, arriving Saturday morning as a Category 1 hurricane with sustained winds of up to 89 mph.

Ernesto still left nearly three-quarters of Bermuda without power as it uprooted trees and flooded streets, but no major injuries or damage was reported. It helped that the vast majority of the 64,000 residents in the archipelago appear to have followed government directives to stay indoors during the height of the storm.

“I'm happy to report that there have been no calls for service for any major incidents or damage to any property, and those calls that we've received over the last six hours or so are primarily flooding," risk management official Lyndon Raynor said in a Saturday update.

Peak of predicted hyperactive hurricane season still ahead

Ernesto is the fifth named storm and third hurricane of the current season, which has yet to reach its peak and is widely expected to be quite a bit more active than the norm. The season runs from June 1 to Nov. 30 and typically reaches its high point from late August through the end of September.

The latest forecast by the National Oceanic and Atmospheric Administration calls for 17-24 named storms and 8-13 hurricanes. The forecast says 4 to 7 of the storms would reach major status, meaning at least a Category 3 hurricane with minimum sustained winds of 111 mph. The yearly averages are 14.4 named storms, 7.2 hurricanes, and 3.2 major ones.

Hurricane Beryl served notice of the season's potential for highly damaging storms, which are being nourished by unusually warm waters in the Atlantic when it became the earliest recorded Category 5 hurricane on July 1. Hurricanes Debby and Ernesto have followed and caused much of their havoc by unloading copious amounts of rain, leading to widespread flooding, more than by blowing away infrastructure with ferocious winds.

Contributing: Mike Snider and Eduardo Cuevas